Structures and reaction mechanisms of GTP cyclohydrolases

Gräwert, Tobias; Fischer, Markus; Bacher, Adelbert

doi:10.1002/iub.1153

Cited by 17 publications

(18 citation statements)

References 49 publications

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“…6A) (21). The first half of the reaction comprises two sequential hydrolysis reactions that result in purine ring opening and release of formic acid to give 2,5-diamino-6-ribosylamino-4(3H)-pyrimidinone 5′-triphosphate (compound II) (Fig.…”

Section: Resultsmentioning

confidence: 99%

Promiscuous and Adaptable Enzymes Fill “Holes” in the Tetrahydrofolate Pathway in Chlamydia Species

Adams

Thiaville

Proestos

et al. 2014

mBio

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Folates are tripartite molecules comprising pterin, para-aminobenzoate (PABA), and glutamate moieties, which are essential cofactors involved in DNA and amino acid synthesis. The obligately intracellular Chlamydia species have lost several biosynthetic pathways for essential nutrients which they can obtain from their host but have retained the capacity to synthesize folate. In most bacteria, synthesis of the pterin moiety of folate requires the FolEQBK enzymes, while synthesis of the PABA moiety is carried out by the PabABC enzymes. Bioinformatic analyses reveal that while members of Chlamydia are missing the genes for FolE (GTP cyclohydrolase) and FolQ, which catalyze the initial steps in de novo synthesis of the pterin moiety, they have genes for the rest of the pterin pathway. We screened a chlamydial genomic library in deletion mutants of Escherichia coli to identify the “missing genes” and identified a novel enzyme, TrpFCtL2, which has broad substrate specificity. TrpFCtL2, in combination with GTP cyclohydrolase II (RibA), the first enzyme of riboflavin synthesis, provides a bypass of the first two canonical steps in folate synthesis catalyzed by FolE and FolQ. Notably, TrpFCtL2 retains the phosphoribosyl anthranilate isomerase activity of the original annotation. Additionally, we independently confirmed the recent discovery of a novel enzyme, CT610, which uses an unknown precursor to synthesize PABA and complements E. coli mutants with deletions of pabA, pabB, or pabC. Thus, Chlamydia species have evolved a variant folate synthesis pathway that employs a patchwork of promiscuous and adaptable enzymes recruited from other biosynthetic pathways.

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Section: Resultsmentioning

confidence: 99%

Promiscuous and Adaptable Enzymes Fill “Holes” in the Tetrahydrofolate Pathway in Chlamydia Species

Adams

Thiaville

Proestos

et al. 2014

mBio

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“…The same reaction is also involved in the biosynthesis of tetrahydrobiopterin ( 227 ), a cofactor required for phenylalanine hydroxylase and nitric oxide synthase, and 7-deazapurine ( 228 ), which is a key component of hypermodified tRNA nucleosides (such as queuosine, 229 ) and nucleoside antibiotics (such as toyocamycin, 230 , Figure 61b). [230] …”

Section: Rearrangementmentioning

confidence: 99%

The Enzymology of Organic Transformations: A Survey of Name Reactions in Biological Systems

2017

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Chemical reactions that are named in honor of their true or at least perceived discoverers are known as “name reactions”. This review is a collection of biological representatives of named chemical reactions. Emphasis is placed on reaction types and catalytic mechanisms that showcase both the chemical diversity in natural product biosynthesis as well as the parallels with synthetic organic chemistry. An attempt has been made to describe the enzymatic mechanisms of catalysis within the context of their synthetic counterparts whenever possible and to discuss the mechanistic hypotheses for those reactions that are presently active areas of investigation. This review has been categorized by reaction type, e.g., condensation, nucleophilic addition, reduction and oxidation, substitution, carboxylation, radical-mediated, and rearrangements, which are subdivided by named reactions.

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“…GCH1 is a well-conserved protein found in bacteria, protozoa, plants and animals including human [26,27]. The enzyme converts GTP into 7,8 dihydroneopterin triphosphate, the precursor of the pterin moiety in folate derivatives (Figure 1) [26].…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…The enzyme converts GTP into 7,8 dihydroneopterin triphosphate, the precursor of the pterin moiety in folate derivatives (Figure 1) [26]. The enzyme forms a homodecameric barrel-like structure with ten zinc-containing active sites with each of them formed between three subunits [26]. The enzyme catalyzes the breakages of the guanine and ribose rings in GTP and rearranges them to form 7,8-dihydroneopterin triphosphate (Figure 1) [26,28].…”

Section: Introductionmentioning

confidence: 99%

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Biochemical and functional characterization of Plasmodium falciparum GTP cyclohydrolase I

Kümpornsin

Kotanan

Chobson

et al. 2014

Malar J

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BackgroundAntifolates are currently in clinical use for malaria preventive therapy and treatment. The drugs kill the parasites by targeting the enzymes in the de novo folate pathway. The use of antifolates has now been limited by the spread of drug-resistant mutations. GTP cyclohydrolase I (GCH1) is the first and the rate-limiting enzyme in the folate pathway. The amplification of the gch1 gene found in certain Plasmodium falciparum isolates can cause antifolate resistance and influence the course of antifolate resistance evolution. These findings showed the importance of P. falciparum GCH1 in drug resistance intervention. However, little is known about P. falciparum GCH1 in terms of kinetic parameters and functional assays, precluding the opportunity to obtain the key information on its catalytic reaction and to eventually develop this enzyme as a drug target.MethodsPlasmodium falciparum GCH1 was cloned and expressed in bacteria. Enzymatic activity was determined by the measurement of fluorescent converted neopterin with assay validation by using mutant and GTP analogue. The genetic complementation study was performed in ∆folE bacteria to functionally identify the residues and domains of P. falciparum GCH1 required for its enzymatic activity. Plasmodial GCH1 sequences were aligned and structurally modeled to reveal conserved catalytic residues.ResultsKinetic parameters and optimal conditions for enzymatic reactions were determined by the fluorescence-based assay. The inhibitor test against P. falciparum GCH1 is now possible as indicated by the inhibitory effect by 8-oxo-GTP. Genetic complementation was proven to be a convenient method to study the function of P. falciparum GCH1. A series of domain truncations revealed that the conserved core domain of GCH1 is responsible for its enzymatic activity. Homology modelling fits P. falciparum GCH1 into the classic Tunnelling-fold structure with well-conserved catalytic residues at the active site.ConclusionsFunctional assays for P. falciparum GCH1 based on enzymatic activity and genetic complementation were successfully developed. The assays in combination with a homology model characterized the enzymatic activity of P. falciparum GCH1 and the importance of its key amino acid residues. The potential to use the assay for inhibitor screening was validated by 8-oxo-GTP, a known GTP analogue inhibitor.

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Structures and reaction mechanisms of GTP cyclohydrolases

Cited by 17 publications

References 49 publications

Promiscuous and Adaptable Enzymes Fill “Holes” in the Tetrahydrofolate Pathway in Chlamydia Species

Promiscuous and Adaptable Enzymes Fill “Holes” in the Tetrahydrofolate Pathway in Chlamydia Species

The Enzymology of Organic Transformations: A Survey of Name Reactions in Biological Systems

Biochemical and functional characterization of Plasmodium falciparum GTP cyclohydrolase I

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